Thatcher wheat line RL6149 carries Lr64 and a second leaf rust resistance gene on chromosome 1DS

Authors: Kolmer, James; BERNARDO, AMY - Kansas State University; Bai, Guihua; HAYDEN, MATTHEW - La Trobe University; ANDERSON, JAMES - University Of Minnesota

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2019
Publication Date: 7/6/2020
Citation: Kolmer, J.A., Bernardo, A.N., Bai, G., Hayden, M.J., Anderson, J.A. 2020. Thatcher wheat line RL6149 carries Lr64 and a second leaf rust resistance gene on chromosome 1DS. Theoretical and Applied Genetics. 132:2809–2814. https://doi.org/10.1007/s00122-019-03389-y.
DOI: https://doi.org/10.1007/s00122-019-03389-y

Interpretive Summary: RL6149, a near-isogenic line of Thatcher wheat, carries leaf rust resistance gene Lr64 on chromosome arm 6AL. The objective of this study was to develop molecular markers that can be easily used to select wheat lines with Lr64. RL6149 was crossed with Thatcher and F2 plants derived from a single F1 plant were advanced to F6 lines by single seed descent. The 100 F6 recombinant inbred lines (RILs) were inoculated with two races of P. triticina that differed widely for virulence in order to identify resistant and susceptible RILs. Thirty RILs that differed for resistance and the parental lines were genotyped with the 90K Infinium iSelect single nucleotide polymorphism (SNP) array to find closely linked markers with Lr64. Seven linked SNPs on chromosome arm 6AL were converted into Kompetitive Allele Specific PCR (KASP) markers that were genotyped on the 100 RILs. A genetic linkage map for the seven KASP markers spanned 19.1 cM on chromosome arm 6AL. KASP marker IWB59855 was tightly linked to Lr64. A second unexpected gene for leaf rust resistance also segregated in the F6 lines. Four KASP markers that spanned 18.6 cM located the gene on chromosome 1DS. The KASP marker IWB38437 was tightly linked to the second leaf rust resistance gene.

Technical Abstract: Leaf rust caused by the fungus Puccinia triticina, is an important disease of wheat in many regions of the world. A selection of wheat, designated as RL6149, has resistance to leaf rust that came from a relative of wheat, called wild emmer. The objectives of this research was to determine which chromosomes carry the resistance gene(s) from wild emmer in RL6149. The leaf rust resistance in RL6149 was determined to be carried on two chromosomes, the long arm of chromosome 6A and the short arm of chromosome 1D. The leaf rust resistance gene on chromosome 6A was given the official designation of Lr64. Closely linked DNA based genetic markers can be used by wheat breeders to select wheat breeding lines that have this resistance gene. The second gene on chromosome 1DS was not expected, since wild emmer does not have the D genome chromosomes. This gene may be a unique leaf rust resistance gene, since other leaf rust resistance genes on 1D did not share genetic markers with RL6149. Closely linked DNA based genetic markers on chromosome 1DS can be used by wheat breeders to select wheat breeding lines with this gene. Both genes give good resistance to the current leaf rust population in the U.S.